Reaction or curing of polymerizable mixtures of polyisocyanates with polyols (referred to as polyurethane precursors) to form polyurethanes is well known in the art. Curing is facilitated by the addition of catalysts or reaction promoters such as tin salts and tertiary amines (see C. Hepburn, "Polyurethane Elastomers", Applied Science, New York, 1982). Such catalysts or reaction promoters provide almost instantaneous curing of the polyurethane precursors; this is not always desirable, especially when the polyurethane precursors are to be used as a coating. Instead it may be useful to use a latent catalyst or latent reaction promoter which can be activated in a controlled fashion at some time after mixing with the polyurethane precursors.
Thermal curing of polyurethane precursors using thermally latent catalysts is known in the art (see for example U.S. Pat. Nos. 4,521,545, and 4,582,861). Photocuring of polyurethane precursors using compounds capable of generating tertiary amine promoters upon irradiation with ultraviolet light is also known (see U.S. Pat. No. 4,369,206 and European Pat. No. 28,696, (1981) (Derwent Abstract).
Photocuring of urethane (meth)acrylates is also well known (see T. A. Speckhard, K. K. S. Hwang, S. B. Lin, S. Y. Tsay, M. Koshiba, Y. S. Ding, S. L. Cooper J. Appl. Polymer Science 1985, 30, 647-666, and references therein; C. Bluestein Polym.-Plast. Technol. Eng. 1981, 17 83-93). This curing method has many shortcomings: it suffers from sensitivity to oxygen; it necessitates ultraviolet light; and it requires modified resins, i.e., (meth)acrylated polyols and/or (meth)acrylated polyisocyanates, with a corresponding change in the polyurethane properties.
Photocuring of polyurethane precursors to polyurethanes using diazonium salts is known (see U.S. Pat. No. 4,544,466). Photocuring of polyurethane precursors to polyurethanes using organotin compounds is also known (see U.S. Pat. No. 4,549,945).
Organometallic complex cations have been described (see European Patent Nos. 109,851 (1984); 094,915 (1983) (Derwent Abstract); and 094,914 (1983) (Derwent Abstract)). Energy polymerizable compositions comprising ionic salts of organometallic complex cations and cationically sensitive materials and the curing thereof has been taught.
What is not known in the art, but what this invention teaches, is energy polymerizable compositions comprising polyurethane precursors and ionic salts of organometallic complex cations and the curing thereof.
Furthermore, this invention describes energy polymerizable compositions which are more photosensitive than those taught in U.S. Pat. Nos. 4,544,466, and 4,549,945.